The present invention generally relates to oil well casing spiders and elevators used in the oil fields to effect the insertion and removal of drill stem and well casing segments, and more particularly to a combined well casing spider and elevator which may be used interchangeably as the spider or the elevator and includes a laterally pivotable gate member which permits ease in the entry and removal of a drill stem and/or well casing segment. In the specification and the appended claims, reference will only be made to the gripping, release, insertion and removal of a well casing, but it is to be expressly understood that the combined well casing spider and elevator according to the invention is not limited in its use to well casings alone and can be used with well casings, drill stems and other pipe or rod-like members.
To effect the lowering and raising of long strings of oil well casings, a spider is conventionally mounted over the rotary on the platform of the oil well drilling derrick. The spider is operable to grip or release a segment of the well casing. An elevator attached to a hoist co-operates with the spider in the lowering and raising of well casing and is also operable to grip or release the well casing. Well casing is removed, for example, by lowering of the elevator so that it can grip the end of the well casing extending above the spider. The spider then releases the well casing and the elevator is hoisted until the end of the next segment of well casing extends above the spider. The spider agains grips the well casing, and the segment removed by the elevator is disconnected by rotating it. This segment can then be off loaded allowing the elevator to be again lowered to grip the end of the well casing projecting above the spider to repeat the process.
Conventionally, a plurality of arcuate wedge-shaped scepter-like elements or slips formed of cast metal such as steel are borne by a spider bowl which is hollow and whose interior surface tapers upwardly and outwardly. These slips ride on the tapered surface of the spider bowl, being normally keyed thereto, and means are provided for simultaneously raising and lowering of the slips in contact with the tapered surface of the hollow spider bowl such that, when the slips are raised, they move radially away from each other to increase the size of the opening defined by the slips through which passes the well casing. One such type of well spider is shown in U.S. Pat. No. 2,274,273, issued Feb. 24, 1942, to Earl J. Miller.
While the well spider of that construction functions adequately to perform its given task, it is necessary to physically shift the spider between extreme vertical heights with respect to the well casing, normally requiring the unit to be raised above the upper end of the well casing or well casing sections to be gripped prior to lowering the spider into position. Moreover, while the elevator performs a similar, co-operating gripping function, the construction of the elevator is quite different from that of the spider, the two not being interchangeable, requiring on-site spares for each. Further, the mechanical actuating and slip interior section mechanism is generally out of direct access making it both difficult and dangerous to repair or adjust the mechanism or replace a damaged slip.